Ethylene is a precursor to many industrially important chemicals, such as polyethylene, polystyrene, polyvinyl chloride (PVC), and the like, and is primarily manufactured via high-temperature steam cracking of naphtha. The steam cracking process requires high temperatures (>900° C.) and energy for both the reaction and the product separation processes, and as such is among the largest consumers of fuel as well as the largest CO2 emitter of any commodity chemical process.
Methane is the main constituent of natural gas (typically comprising more than 95 percent), for which the reserves are vast and estimated to exceed those of crude oil. Thus, there is great motivation to develop processes for converting methane into higher valued products. Currently, natural gas is primarily used for power generation, residential uses, and industrial applications, including synthetic gas production.
Thus, the oxidative coupling of methane (OCM) is an attractive alternative for the production of C2+ hydrocarbons, as illustrated by Eq. 1:

In the OCM process, CH4 is activated heterogeneously on the catalyst surface to yield methyl radicals. The methyl radicals are then able to participate in several gas phase and heterogeneous reactions yielding various products, thereby defining the reaction selectivity. Two methyl radicals may couple in the gas phase and on the catalyst surface to form ethane, which subsequently may undergo dehydrogenation to form ethylene. Carbon oxides may be formed from methane as well, as ethane and ethylene. A conversion-selectivity trend has been observed, wherein a high CH4/O2 ratio generally leads to high selectivity at low methane conversion, while a lower CH4/O2 leads to high CH4 conversion with lower C2 selectivity, thereby limiting C2 yields. Thus, it is important to optimize the CH4/O2 ratio to achieve high C2 yields.
One problem with catalyst materials has been their deactivation or degradation over time. For example, catalyst materials synthesized by traditional methods, such as by the incipient wetness impregnation method, have preferential enrichment of active components on the catalyst surface. This configuration leads to loss of catalyst efficacy with time on-stream as the surface is ablated and the exposed surface material composition changes.
Thus, there is a need for a catalyst system that is more resistive to degradation. The present novel technology addresses this need.